An axial flow fan and a diagonal flow fan include an impeller including a boss that is a rotation center and a plurality of blades that are provided at an outer peripheral surface of the boss. Hitherto, various structures thereof have been proposed. For example, Patent Literature 1 describes an axial flow fan including inner stationary blades that are connected to a base portion of a motor unit, outer stationary blades that are connected to an inner surface of a housing, and a ring-shaped connecting portion that connects the inner stationary blades and the outer stationary blades. In the axial flow fan described in Patent Literature 1, the blade width of each outer stationary blade is larger than the blade width of each inner stationary blade, and the inclination of each outer stationary blade with respect to a direction of a central axis is equal to the inclination of each inner stationary blade. In this way, when the blade width of each inner stationary blade is smaller than the blade width of each outer stationary blade, in a region away from the central axis, a component that swirls in a circumferential direction of air current is efficiently converted into a component in the direction of the central axis by the outer stationary blades, and, in a region close to the central axis, the influence of resistance that the air current is subjected to can be reduced. Therefore, a sufficient air collection effect is provided by the outer stationary blades, and interference of the inner stationary blades with the air current is suppressed, so that static pressure-air volume characteristics of the axial flow fan are improved.